Additive manufacturing systems often utilize powdered, pulverant materials. An additive manufacturing system is one which selectively builds up a desired article. Known additive manufacturing systems include those using stereolithography, direct metal laser sintering, selective laser sintering, laser engineered net shaping, electron beam melting, laser powder deposition, and e-beam wire melting techniques, among others.
Several known additive manufacturing systems require pulverant feedstock. For example, direct metal laser sintering is used to construct finished parts from a stack of sintered layers of a pulverant metal. In general, finer pulverant material allows for thinner layers to be sintered, which in turn allows for ever-finer features to be constructed. However, finer pulverant material also results in higher surface area of the feedstock material. Higher surface area results in high absorption rates of contaminants. For example, pulverant Nickel-based superalloys often contain oxygen content in the range of 250 ppm or higher.
While pulverant feedstock is generally kept in an inert atmosphere, greater surface area presents a greater challenge for keeping the pulverant feedstock contaminant-free. In applications where the feedstock must have a low level of impurities such as oxygen, hydrogen, or carbonaceous gases, increasing surface area presents a challenge.